ext4: Use atomic_t's in struct flex_groups

Reduce pressure on the sb_bgl_lock family of locks by using atomic_t's
to track the number of free blocks and inodes in each flex_group.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 3 insertions, 6 deletions

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index c4c430977622..e72c72a0b807 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -3044,9 +3044,8 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
         if (sbi->s_log_groups_per_flex) {
                 ext4_group_t flex_group = ext4_flex_group(sbi,
                                                           ac->ac_b_ex.fe_group);
-                spin_lock(sb_bgl_lock(sbi, flex_group));
-                sbi->s_flex_groups[flex_group].free_blocks -= ac->ac_b_ex.fe_len;
-                spin_unlock(sb_bgl_lock(sbi, flex_group));
+                atomic_sub(ac->ac_b_ex.fe_len,
+                           &sbi->s_flex_groups[flex_group].free_blocks);
         }
 
         err = ext4_handle_dirty_metadata(handle, NULL, bitmap_bh);
@@ -4884,9 +4883,7 @@ do_more:
 
         if (sbi->s_log_groups_per_flex) {
                 ext4_group_t flex_group = ext4_flex_group(sbi, block_group);
-                spin_lock(sb_bgl_lock(sbi, flex_group));
-                sbi->s_flex_groups[flex_group].free_blocks += count;
-                spin_unlock(sb_bgl_lock(sbi, flex_group));
+                atomic_add(count, &sbi->s_flex_groups[flex_group].free_blocks);
         }
 
         ext4_mb_release_desc(&e4b);